If you used the "gasket" that came in your gasket kit, the source of your leaking oil pan has been found.
Toyota never, ever used a gasket on the pan for the 7MGTE that I know of. FIPG, or sealer is all they used.
Some bright soul decided to include a pan gasket in the vast majority of rebuild gasket kits, and now leaking 7M's are dripping all over the planet.... LOL
Dropping the pan is a PITA, but better than pulling the motor time wise. (Drop the engine/suspension cradle down slightly like the TSRM notes, and you can do it with the engine in place. You will need to support the engine from above however.....)
This time, use "The Right Stuff" to seal up your pan, and burn your cork gasket. (I now have a leak free 7MGTE assembled with "The Right Stuff" everywhere all the crappy paper gaskets normally go. No leaks now. No leaks ever. (Assuming the engine lasts that long of course....)
Only seals you need are the cams, front and rear mains, oil pump drive, cams and cam cover seals. Gaskets that are nice to have include exhaust, intake and that's it. (And if you want your valve covers to not leak, run a small bead of the right stuff around the inside of the rubber seal, and then put them in place on a clean head. No leaks.)
Good luck. The best news is the can of "The Right Stuff" is like 15.00, and looks like black cheese whiz when you dispense it. (Very easy to get either a nice thin bead if you go faster, and thick beads when you move the can/tip slower....) Can't get any easier.